Molecular targets for cannabidiol and its synthetic analogues: effect on vanilloid VR1 receptors and on the cellular uptake and enzymatic hydrolysis of anandamide

Cannabidiol-induced intracellular Ca2+ elevations in hippocampal cells

The phytocannabinoid cannabidiol (CBD) is at the forefront of therapeutic cannabinoid research due to its non-psychotropic properties. Research supports its use in a variety of disorders, yet the cellular mechanisms of its action remain unclear. In this study, the effect of CBD upon Ca2+ homeostasis in hippocampal cells was characterised. CBD (1 microM) elevated intracellular Ca2+ ([Ca2+]i) by approximately +45% of basal Ca2+ levels in both glia (77% responders) and neurones (51% responders). Responses to CBD were reduced in high excitability HEPES buffered solution (HBS), but not affected in low excitability/low Ca2+ HBS. CBD responses were also significantly reduced (by 50%) by the universal Ca2+ channel blocker cadmium (50 microM) and the L-type specific Ca2+ channel blocker nifedipine (20 microM). Interestingly, intracellular store depletion with thapsigargin (2 microM) had the most dramatic effect on CBD responses, leading on average to a full block of the response. Elevated CBD-induced [Ca2+]i responses (>+100%) were observed in the presence of the CB1 receptor antagonist, AM281 (1 microM), and the vanilloid receptor antagonist, capsazepine (CPZ, 1 microM). Overall, our data suggest that CBD modulates hippocampal [Ca2+]i homeostasis via intracellular Ca2+ stores and L-type VGCC-mediated Ca2+ entry, with tonic cannabinoid and vanilloid receptor signalling being negatively coupled to this pathway.

Pharmacological actions of cannabinoids

Mammalian tissues express at least two types of cannabinoid receptor, CB1 and CB2, both G protein coupled. CB1 receptors are expressed predominantly at nerve terminals where they mediate inhibition of transmitter release. CB2 receptors are found mainly on immune cells, one of their roles being to modulate cytokine release. Endogenous ligands for these receptors (endocannabinoids) also exist. These are all eicosanoids; prominent examples include arachidonoylethanolamide (anandamide) and 2-arachidonoyl glycerol. These discoveries have led to the development of CB1- and CB2-selective agonists and antagonists and of bioassays for characterizing such ligands. Cannabinoid receptor antagonists include the CB1-selective SR141716A, AM251, AM281 and LY320135, and the CB2-selective SR144528 and AM630. These all behave as inverse agonists, one indication that CB1 and CB2 receptors can exist in a constitutively active state. Neutral cannabinoid receptor antagonists that seem to lack inverse agonist properties have recently also been developed. As well as acting on CB1 and CB2 receptors, there is convincing evidence that anandamide can activate transient receptor potential vanilloid type 1 (TRPV1) receptors. Certain cannabinoids also appear to have non-CB1, non-CB2, non-TRPV1 targets, for example CB2-like receptors that can mediate antinociception and "abnormal-cannabidiol" receptors that mediate vasorelaxation and promote microglial cell migration. There is evidence too for TRPV1-like receptors on glutamatergic neurons, for alpha2-adrenoceptor-like (imidazoline) receptors at sympathetic nerve terminals, for novel G protein-coupled receptors for R-(+)-WIN55212 and anandamide in the brain and spinal cord, for novel receptors for delta9-tetrahydrocannabinol and cannabinol on perivascular sensory nerves and for novel anandamide receptors in the gastro-intestinal tract. The presence of allosteric sites for cannabinoids on various ion channels and non-cannabinoid receptors has also been proposed. In addition, more information is beginning to emerge about the pharmacological actions of the non-psychoactive plant cannabinoid, cannabidiol. These recent advances in cannabinoid pharmacology are all discussed in this review.

A tale of two cannabinoids: the therapeutic rationale for combining tetrahydrocannabinol and cannabidiol

This study examines the current knowledge of physiological and clinical effects of tetrahydrocannabinol (THC) and cannabidiol (CBD) and presents a rationale for their combination in pharmaceutical preparations. Cannabinoid and vanilloid receptor effects as well as non-receptor mechanisms are explored, such as the capability of THC and CBD to act as anti-inflammatory substances independent of cyclo-oxygenase (COX) inhibition. CBD is demonstrated to antagonise some undesirable effects of THC including intoxication, sedation and tachycardia, while contributing analgesic, anti-emetic, and anti-carcinogenic properties in its own right. In modern clinical trials, this has permitted the administration of higher doses of THC, providing evidence for clinical efficacy and safety for cannabis based extracts in treatment of spasticity, central pain and lower urinary tract symptoms in multiple sclerosis, as well as sleep disturbances, peripheral neuropathic pain, brachial plexus avulsion symptoms, rheumatoid arthritis and intractable cancer pain. Prospects for future application of whole cannabis extracts in neuroprotection, drug dependency, and neoplastic disorders are further examined. The hypothesis that the combination of THC and CBD increases clinical efficacy while reducing adverse events is supported.

Anandamide acts as an intracellular messenger amplifying Ca2+ influx via TRPV1 channels

The endocannabinoid anandamide is able to interact with the transient receptor potential vanilloid 1 (TRPV1) channels at a molecular level. As yet, endogenously produced anandamide has not been shown to activate TRPV1, but this is of importance to understand the physiological function of this interaction. Here, we show that intracellular Ca2+ mobilization via the purinergic receptor agonist ATP, the muscarinic receptor agonist carbachol or the Ca(2+)-ATPase inhibitor thapsigargin leads to formation of anandamide, and subsequent TRPV1-dependent Ca2+ influx in transfected cells and sensory neurons of rat dorsal root ganglia (DRG). Anandamide metabolism and efflux from the cell tonically limit TRPV1-mediated Ca2+ entry. In DRG neurons, this mechanism was found to lead to TRPV1-mediated currents that were enhanced by selective blockade of anandamide cellular efflux. Thus, endogenous anandamide is formed on stimulation of metabotropic receptors coupled to the phospholipase C/inositol 1,4,5-triphosphate pathway and then signals to TRPV1 channels. This novel intracellular function of anandamide may precede its action at cannabinoid receptors, and might be relevant to its control over neurotransmitter release.

Agonistic Properties of Cannabidiol at 5-HT1a Receptors

Cannabidiol (CBD) is a major, biologically active, but psycho-inactive component of cannabis. In this cell culture-based report, CBD is shown to displace the agonist, [3H]8-OH-DPAT from the cloned human 5-HT1a receptor in a concentration-dependent manner. In contrast, the major psychoactive component of cannabis, tetrahydrocannabinol (THC) does not displace agonist from the receptor in the same micromolar concentration range. In signal transduction studies, CBD acts as an agonist at the human 5-HT1a receptor as demonstrated in two related approaches. First, CBD increases [35S]GTPgammaS binding in this G protein coupled receptor system, as does the known agonist serotonin. Second, in this GPCR system, that is negatively coupled to cAMP production, both CBD and 5-HT decrease cAMP concentration at similar apparent levels of receptor occupancy, based upon displacement data. Preliminary comparative data is also presented from the cloned rat 5-HT2a receptor suggesting that CBD is active, but less so, relative to the human 5-HT1a receptor, in binding analyses. Overall, these studies demonstrate that CBD is a modest affinity agonist at the human 5-HT1a receptor. Additional work is required to compare CBD's potential at other serotonin receptors and in other species. Finally, the results indicate that cannabidiol may have interesting and useful potential beyond the realm of cannabinoid receptors.

Cannabidiol inhibits human glioma cell migration through a cannabinoid receptor-independent mechanism

We evaluated the ability of cannabidiol (CBD) to impair the migration of tumor cells stimulated by conditioned medium. CBD caused concentration-dependent inhibition of the migration of U87 glioma cells, quantified in a Boyden chamber. Since these cells express both cannabinoid CB1 and CB2 receptors in the membrane, we also evaluated their engagement in the antimigratory effect of CBD. The inhibition of cell was not antagonized either by the selective cannabinoid receptor antagonists SR141716 (CB1) and SR144528 (CB2) or by pretreatment with pertussis toxin, indicating no involvement of classical cannabinoid receptors and/or receptors coupled to Gi/o proteins. These results reinforce the evidence of antitumoral properties of CBD, demonstrating its ability to limit tumor invasion, although the mechanism of its pharmacological effects remains to be clarified.

Cannabinoids provide neuroprotection against 6-hydroxydopamine toxicity in vivo and in vitro: relevance to Parkinson's disease

Cannabinoids have been reported to provide neuroprotection in acute and chronic neurodegeneration. In this study, we examined whether they are also effective against the toxicity caused by 6-hydroxydopamine, both in vivo and in vitro, which may be relevant to Parkinson's disease (PD). First, we evaluated whether the administration of cannabinoids in vivo reduces the neurodegeneration produced by a unilateral injection of 6-hydroxydopamine into the medial forebrain bundle. As expected, 2 weeks after the application of this toxin, a significant depletion of dopamine contents and a reduction of tyrosine hydroxylase activity in the lesioned striatum were noted, and were accompanied by a reduction in tyrosine hydroxylase-mRNA levels in the substantia nigra. None of these events occurred in the contralateral structures. Daily administration of delta9-tetrahydrocannabinol (delta9-THC) during these 2 weeks produced a significant waning in the magnitude of these reductions, whereas it failed to affect dopaminergic parameters in the contralateral structures. This effect of delta9-THC appeared to be irreversible since interruption of the daily administration of this cannabinoid after the 2-week period did not lead to the re-initiation of the 6-hydroxydopamine-induced neurodegeneration. In addition, the fact that the same neuroprotective effect was also produced by cannabidiol (CBD), another plant-derived cannabinoid with negligible affinity for cannabinoid CB1 receptors, suggests that the antioxidant properties of both compounds, which are cannabinoid receptor-independent, might be involved in these in vivo effects, although an alternative might be that the neuroprotection exerted by both compounds might be due to their anti-inflammatory potential. As a second objective, we examined whether cannabinoids also provide neuroprotection against the in vitro toxicity of 6-hydroxydopamine. We found that the non-selective cannabinoid agonist HU-210 increased cell survival in cultures of mouse cerebellar granule cells exposed to this toxin. However, this effect was significantly lesser when the cannabinoid was directly added to neuronal cultures than when these cultures were exposed to conditioned medium obtained from mixed glial cell cultures treated with HU-210, suggesting that the cannabinoid exerted its major protective effect by regulating glial influence to neurons. In summary, our results support the view of a potential neuroprotective action of cannabinoids against the in vivo and in vitro toxicity of 6-hydroxydopamine, which might be relevant for PD. Our data indicated that these neuroprotective effects might be due, among others, to the antioxidant properties of certain plant-derived cannabinoids, or exerted through the capability of cannabinoid agonists to modulate glial function, or produced by a combination of both mechanisms.

Effect of the cannabinoid ajulemic acid on rat models of neuropathic and inflammatory pain

There is increasing evidence that cannabinoid agonists alleviate the abnormal pain sensations associated with animal models of neuropathic and inflammatory pain. However, cannabinoids produce a number of motor and psychotropic side effects. In the present study we found that systemic administration of the cannabinoid acid derivative 1',1'-dimethylheptyl-delta-8-tetrahydrocannabinol-11-oic acid (ajulemic acid, IP-751) and the non-selective cannabinoid receptor agonist HU-210 reduced mechanical allodynia in a nerve-injury induced model of neuropathic pain and in the CFA-induced model of inflammatory pain. In contrast, HU-210, but not ajulemic acid reduced motor performance in the rotarod test. These findings suggest that ajulemic acid reduces abnormal pain sensations associated with chronic pain without producing the motor side effects associated with THC and other non-selective cannabinoid receptor agonists.

The safety of cannabinoids for the treatment of multiple sclerosis

The evidence for the therapeutic efficacy of cannabinoids in the treatment of multiple sclerosis (MS) is increasing but is not as yet convincing. Although several trials have reported no significant effect, the majority of the evidence which supports a beneficial effect on spasticity and pain is based on subjective measurements in trials where unblinding was likely to be a problem. The available clinical trial data suggest that the adverse side effects associated with using cannabis-based medicinal extracts (CBMEs) are generally mild, such as dry mouth, dizziness, somnolence, nausea and intoxication, and in no case did toxicity develop. However, most of these trials were run over a period of months and it is possible that other adverse side effects, not seen in these short-term studies, could develop with long-term use. Despite the evidence that cannabinoids can disrupt cognitive function and promote depression, on the basis of current data, such adverse effects seem unlikely to be associated with the use of CBMEs. Likewise, there is no evidence to suggest that their effects on balance and motor control, or immune function, may be clinically significant. There is, however, reason to be concerned about the use of therapeutic cannabinoids by people predisposed to psychosis and by pregnant women, given the increasing evidence of their adverse effects on the fetus. In conclusion, given the modest therapeutic effects of cannabinoids demonstrated so far, and the risk of long-term adverse side effects, there is reason to be cautious about their use in the treatment of MS.

Cannabidiol Prevents Cerebral Infarction Via a Serotonergic 5-Hydroxytryptamine 1A Receptor–Dependent Mechanism

Background and Purpose— Cannabidiol has been reported to be a neuroprotectant, but the neuroprotective mechanism of cannabidiol remains unclear. We studied the neuroprotective mechanism of cannabidiol in 4-hour middle cerebral artery (MCA) occlusion mice.

Methods— Male MCA occluded mice were treated with cannabidiol, abnormal cannabidiol, anandamide, methanandamide, cannabidiol plus capsazepine, and cannabidiol plus WAY100135 before and 3 hours after MCA occlusion. The infarct size was determined after 24 hours (2,3,5-triphenyltetrazolium chloride staining). Cerebral blood flow (CBF) was measured at, before and 1, 2, 3, and 4 hours after MCA occlusion.

Results— Cannabidiol significantly reduced the infarct volume induced by MCA occlusion in a bell-shaped curve. Similarly, abnormal cannabidiol but not anandamide or methanandamide reduced the infarct volume. Moreover, the neuroprotective effect of cannabidiol was inhibited by WAY100135, a serotonin 5-hydroxytriptamine 1A (5-HT 1A ) receptor antagonist but not capsazepine a vanilloid receptor antagonist. Cannabidiol increased CBF to the cortex, and the CBF was partly inhibited by WAY100135 in mice subjected to MCA occlusion.

Conclusions— Cannabidiol and abnormal cannabidiol reduced the infarct volume. Furthermore, the neuroprotective effect of cannabidiol was inhibited by WAY100135 but not capsazepine, and the CBF increased by cannabidiol was partially reversed by WAY100135. These results suggested that the neuroprotective effect of cannabidiol may be related to the increase in CBF through the serotonergic 5-HT 1A receptor.

Cannabinoids in bipolar affective disorder: a review and discussion of their therapeutic potential

Bipolar affective disorder is often poorly controlled by prescribed drugs. Cannabis use is common in patients with this disorder and anecdotal reports suggest that some patients take it to alleviate symptoms of both mania and depression. We undertook a literature review of cannabis use by patients with bipolar disorder and of the neuropharmacological properties of cannabinoids suggesting possible therapeutic effects in this condition. No systematic studies of cannabinoids in bipolar disorder were found to exist, although some patients claim that cannabis relieves symptoms of mania and/or depression. The cannabinoids Delta(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD) may exert sedative, hypnotic, anxiolytic, antidepressant, antipsychotic and anticonvulsant effects. Pure synthetic cannabinoids, such as dronabinol and nabilone and specific plant extracts containing THC, CBD, or a mixture of the two in known concentrations, are available and can be delivered sublingually. Controlled trials of these cannabinoids as adjunctive medication in bipolar disorder are now indicated.

Emerging properties of cannabinoid medicines in management of multiple sclerosis

Use of cannabis as a medicine for numerous conditions has a well-documented history stretching back thousands of years. With the identification of an endogenous system of receptors and ligands in recent years, abundant experimental data have reinforced the anecdotal claims of people who perceive medicinal benefit from the currently illegal consumption of cannabis. This, combined with data from recent clinical trials, points to the prospect of cannabis as a medication in the treatment of multiple sclerosis and numerous other medical conditions.

Peripheral, but not central effects of cannabidiol derivatives: mediation by CB(1) and unidentified receptors

Delta-9 tetrahydrocannabinol (Delta(9)-THC) and (-)-cannabidiol ((-)-CBD) are major constituents of the Cannabis sativa plant with different pharmacological profiles: (Delta(9)-THC activates cannabinoid CB(1) and CB(2) receptors and induces psychoactive and peripheral effects. (-)-CBD possesses no, or very weak affinity for these receptors. We tested a series of (+)- and (-)-CBD derivatives for central and peripheral effects in mice. None of the (-)-CBD derivatives were centrally active, yet most inhibited intestinal motility. Of the five (+)-CBD derivatives, all with CB(1) receptor affinity, only (+)-7-OH-CBD-DMH (DMH=1,1-dimethylheptyl), acted centrally, while all five arrested defecation. The effects of (+)-CBD-DMH and (+)-7-OH-CBD-DMH were inhibited by the CB(1) receptor antagonist SR141716. The CB(2) receptor antagonist SR144528, and the vanilloid TRPV1 receptor antagonist capsazepine, had no influence. Further, the (-)-CBD derivatives (-)-7-COOH-CBD and (-)-7-COOH-CBD-DMH, displayed antiinflammatory activity. We suggest that (+)-CBD analogues have mixed agonist/antagonist activity in the brain. Second, (-)-CBD analogues which are devoid of cannabinoid receptor affinity but which inhibit intestinal motility, suggest the existence of a non-CB(1), non-CB(2) receptor. Therefore, such analogues should be further developed as antidiarrheal and/or antiinflammatory drugs. We propose to study the therapeutic potential of (-)- and (+)-CBD derivatives for complex conditions such as inflammatory bowel disease and cystic fibrosis.

Cannabidiol inhibits the hyperlocomotion induced by psychotomimetic drugs in mice

Cannabidiol is a non-psychotomimetic compound from Cannabis sativa. It is proposed as a possible antipsychotic drug, since it can prevent some psychotomimetic-like effects of Delta9-tetrahydrocannabinol or apomorphine. Therefore, the aim of this work was to test the hypothesis that cannabidiol would inhibit the hyperlocomotion induced by two psychotomimetic drugs, D-amphetamine or ketamine. Male Swiss mice received i.p. injections of haloperidol (0.15-0.6 mg/kg), clozapine (1.25-5 mg/kg) or cannabidiol (15-60 mg/kg) followed by D-amphetamine (5 mg/kg) or ketamine (60 mg/kg). Thirty minutes after the first injection, the distance moved in circular arena was measured during 10 min. In another group of experiments, catalepsy was measured 30 min after haloperidol, clozapine or cannabidiol injections. Cannabidiol, like clozapine but unlike haloperidol, inhibited hyperlocomotion without inducing catalepsy. Moreover, cannabidiol itself, unlike haloperidol and clozapine, did not decrease locomotion. In conclusion, cannabidiol exhibits an antipsychotic-like profile without inducing extrapyramidal-like effects.

Evidence that (-)-7-hydroxy-4'-dimethylheptyl-cannabidiol activates a non-CB(1), non-CB(2), non-TRPV1 target in the mouse vas deferens

Previous experiments showed that R-(+)-WIN55212-induced inhibition of electrically-evoked contractions of mouse vasa deferentia could be antagonized by cannabidiol in a manner that appeared to be competitive but not to involve direct competition for established cannabinoid receptors. We have now discovered that (-)-7-hydroxy-4'-dimethylheptyl-cannabidiol (7-OH-DMH-CBD) inhibits electrically-evoked contractions of the vas deferens (EC(50)=13.3 nM). This it appeared to do by acting on prejunctional neurones as 100 nM 7-OH-DMH-CBD did not attenuate contractile responses to phenylephrine or beta,gamma-methylene-ATP. Although 7-OH-DMH-CBD was antagonized by SR141716A, it was less susceptible to antagonism by this CB(1) receptor antagonist than R-(+)-WIN55212. 7-OH-DMH-CBD was also antagonized by cannabidiol (1 microM; apparent K(B)=222.2 nM) but not by the CB(2) receptor antagonist, SR144528 (32 nM), or by naloxone (300 nM), ruthenium red (1 microM) or capsazepine (10 microM). Yohimbine (100 nM) enhanced the ability of 7-OH-DMH-CBD to inhibit electrically-evoked contractions. R-(+)-WIN55212 was also potentiated by 100 nM yohimbine, possibly reflecting ongoing sequestration of G(i/o) proteins from CB(1) receptors by alpha(2)-adrenoceptors. Our results suggest that 7-OH-DMH-CBD may activate a neuronal target in the vas deferens that is not a CB(1), CB(2), TRPV1, opioid or alpha(2)-adrenergic receptor but do not exclude the possibility that it also activates CB(1) receptors.

Cardiovascular pharmacology of cannabinoids

Cannabinoids and their synthetic and endogenous analogs affect a broad range of physiological functions, including cardiovascular variables, the most important component of their effect being profound hypotension. The mechanisms of the cardiovascular effects of cannabinoids in vivo are complex and may involve modulation of autonomic outflow in both the central and peripheral nervous systems as well as direct effects on the myocardium and vasculature. Although several lines of evidence indicate that the cardiovascular depressive effects of cannabinoids are mediated by peripherally localized CB1 receptors, recent studies provide strong support for the existence of as-yet-undefined endothelial and cardiac receptor(s) that mediate certain endocannabinoid-induced cardiovascular effects. The endogenous cannabinoid system has been recently implicated in the mechanism of hypotension associated with hemorrhagic, endotoxic, and cardiogenic shock, and advanced liver cirrhosis. Furthermore, cannabinoids have been considered as novel antihypertensive agents. A protective role of endocannabinoids in myocardial ischemia has also been documented. In this chapter, we summarize current information on the cardiovascular effects of cannabinoids and highlight the importance of these effects in a variety of pathophysiological conditions.

Enantiomeric cannabidiol derivatives: synthesis and binding to cannabinoid receptors

(-)-Cannabidiol (CBD) is a major, non psychotropic constituent of cannabis. It has been shown to cause numerous physiological effects of therapeutic importance. We have reported that CBD derivatives in both enantiomeric series are of pharmaceutical interest. Here we describe the syntheses of the major CBD metabolites, (-)-7-hydroxy-CBD and (-)-CBD-7-oic acid and their dimethylheptyl (DMH) homologs, as well as of the corresponding compounds in the enantiomeric (+)-CBD series. The starting materials were the respective CBD enantiomers and their DMH homologs. The binding of these compounds to the CB(1) and CB(2) cannabinoid receptors are compared. Surprisingly, contrary to the compounds in the (-) series, which do not bind to the receptors, most of the derivatives in the (+) series bind to the CB(1) receptor in the low nanomole range. Some of these compounds also bind weakly to the CB(2) receptor.

Structural requirements for cannabinoid receptor probes

The discovery and cloning of CB1 and CB2, the two known G(i/o) protein-coupled cannabinoid receptors, as well as the isolation and characterization of two families of endogenous cannabinergic ligands represented by arachidonoylethanolamide (anandamide) and 2-arachidonoylglycerol (2-AG), have opened new horizons in this newly discovered field of biology. Furthermore, a considerable number of cannabinoid analogs belonging to structurally diverse classes of compounds have been synthesized and tested, thus providing substantial information on the structural requirements for cannabinoid receptor recognition and activation. Experiments with site-directed mutated receptors and computer modeling studies have suggested that these diverse classes of ligands may interact with the receptors through different binding motifs. The information about the exact binding site may be obtained with the help of suitably designed molecular probes. These ligands either interact with the receptors in a reversible fashion (reversible probes) or alternatively attach at or near the receptor active site with the formation of covalent bonds (irreversible probes). This review focuses on structural requirements of cannabinoid receptor ligands and highlights their pharmacological and therapeutic potential.

Survey on cannabis use in Parkinson's disease: subjective improvement of motor symptoms

An anonymous questionnaire sent to all patients attending the Prague Movement Disorder Centre revealed that 25% of 339 respondents had taken cannabis and 45.9% of these described some form of benefit.

(+)-Cannabidiol analogues which bind cannabinoid receptors but exert peripheral activity only

Delta9-Tetrahydrocannabinol (Delta9-THC) and (-)-cannabidiol are major constituents of the Cannabis sativa plant with different pharmacological profiles: (-)-Delta9-tetrahydrocannabinol, but not (-)-cannabidiol, activates cannabinoid CB1 and CB2 receptors and induces psychoactive and peripheral effects. We have tested a series of (+)-cannabidiol derivatives, namely, (+)-cannabidiol-DMH (DMH-1,1-dimethylheptyl-), (+)-7-OH-cannabidiol-DMH, (+)-7-OH- cannabidiol, (+)-7-COOH- cannabidiol and (+)-7-COOH-cannabidiol-DMH, for central and peripheral (intestinal, antiinflammatory and peripheral pain) effects in mice. Although all (+)-cannabidiols bind to cannabinoid CB1 and CB2 receptors, only (+)-7-OH-cannabidiol-DMH was centrally active, while all (+)-cannabidiol analogues completely arrested defecation. The effects of (+)-cannabidiol-DMH and (+)-7-OH-cannabidiol-DMH were partially antagonized by the cannabinoid CB1 receptor antagonist N-(piperidiny-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716), but not by the cannabinoid CB2 receptor antagonist N-[-(1S)-endo-1,3,3-trimethil bicyclo [2.2.1] heptan-2-yl-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528), and had no effect on CB1(-/-) receptor knockout mice. (+)-Cannabidiol-DMH inhibited the peripheral pain response and arachidonic-acid-induced inflammation of the ear. We conclude that centrally inactive (+)-cannabidiol analogues should be further developed as antidiarrheal, antiinflammatory and analgesic drugs for gastrointestinal and other peripheral conditions.

On-demand activation of the endocannabinoid system in the control of neuronal excitability and epileptiform seizures

Neurons intensively exchange information among each other using both inhibitory and excitatory neurotransmitters. However, if the balance of excitation and inhibition is perturbed, the intensity of excitatory transmission may exceed a certain threshold and epileptic seizures can occur. As the occurrence of epilepsy in the human population is about 1%, the search for therapeutic targets to alleviate seizures is warranted. Extracts of Cannabis sativa have a long history in the treatment of various neurological diseases, including epilepsy. However, cannabinoids have been reported to exert both pro- and anti-convulsive activities. The recent progress in understanding the endogenous cannabinoid system has allowed new insights into these opposing effects of cannabinoids. When excessive neuronal activity occurs, endocannabinoids are generated on demand and activate cannabinoid type 1 (CB1) receptors. Using mice lacking CB1 receptors in principal forebrain neurons in a model of epileptiform seizures, it was shown that CB1 receptors expressed on excitatory glutamatergic neurons mediate the anti-convulsive activity of endocannabinoids. Systemic activation of CB1 receptors by exogenous cannabinoids, however, are anti- or pro-convulsive, depending on the seizure model used. The pro-convulsive activity of exogenous cannabinoids might be explained by the notion that CB1 receptors expressed on inhibitory GABAergic neurons are also activated, leading to a decreased release of GABA, and to a concomitant increase in seizure susceptibility. The concept that the endogenous cannabinoid system is activated on demand suggests that a promising strategy to alleviate seizure frequency is the enhancement of endocannabinoid levels by inhibiting the cellular uptake and the degradation of these endogenous compounds.

Cannabidiol prevents infarction via the non-CB1 cannabinoid receptor mechanism

Cannabidiol, a non-psychoactive constituent of cannabis, has been reported as a neuroprotectant. Cannabidiol and Delta(9)-tetrahydrocannabinol, the primary psychoactive constituent of cannabis, significantly decreased the infarct volume at 4 h in the mouse middle cerebral artery occlusion model. The neuroprotective effects of Delta(9)-tetrahydrocannabinol but not cannabidiol were inhibited by SR141716, a cannabinoid CB1 receptor antagonist, and were abolished by warming of the animals to the levels observed in the controls. Delta(9)-Tetrahydrocannabinol significantly decreased the rectal temperature, and the hypothermic effect was inhibited by SR141716. These results surely show that the neuroprotective effect of Delta(9)-tetrahydrocannabinol are via a CB1 receptor and temperature-dependent mechanisms whereas the neuroprotective effects of cannabidiol are independent of CB1 blockade and of hypothermia.

The endocannabinoid system and its therapeutic exploitation

The term 'endocannabinoid' - originally coined in the mid-1990s after the discovery of membrane receptors for the psychoactive principle in Cannabis, Delta9-tetrahydrocannabinol and their endogenous ligands - now indicates a whole signalling system that comprises cannabinoid receptors, endogenous ligands and enzymes for ligand biosynthesis and inactivation. This system seems to be involved in an ever-increasing number of pathological conditions. With novel products already being aimed at the pharmaceutical market little more than a decade since the discovery of cannabinoid receptors, the endocannabinoid system seems to hold even more promise for the future development of therapeutic drugs. We explore the conditions under which the potential of targeting the endocannabinoid system might be realized in the years to come.

Vanilloid TRPV1 receptor mediates the antihyperalgesic effect of the nonpsychoactive cannabinoid, cannabidiol, in a rat model of acute inflammation

Cannabidiol (CBD), a nonpsychoactive marijuana constituent, was recently shown as an oral antihyperalgesic compound in a rat model of acute inflammation. We examined whether the CBD antihyperalgesic effect could be mediated by cannabinoid receptor type 1 (CB1) or cannabinoid receptor type 2 (CB2) and/or by transient receptor potential vanilloid type 1 (TRPV1). Rats received CBD (10 mg kg(-1)) and the selective antagonists: SR141716 (N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide) for CB1, SR144528 (N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3 carboxamide) for CB2 and capsazepine (CPZ) for TRPV1 receptors. The intraplantar injection of carrageenan in rats induced a time-dependent thermal hyperalgesia, which peaked at 3 h and decreased at the following times. CBD, administered 2 h after carrageenan, abolished the hyperalgesia to the thermal stimulus evaluated by plantar test. Neither SR141716 (0.5 mg kg(-1)) nor SR144528 (3 and 10 mg kg(-1)) modified the CBD-induced antihyperalgesia; CPZ partially at the lowest dose (2 mg kg(-1)) and fully at the highest dose (10 mg kg(-1)) reversed this effect. These results demonstrate that TRPV1 receptor could be a molecular target of the CBD antihyperalgesic action.

Cannabidiol lacks the vanilloid VR1-mediated vasorespiratory effects of capsaicin and anandamide in anaesthetised rats

The results of vasorespiratory studies in rats anaesthetised with pentobarbital show that (+/-) cannabidiol, a cannabinoid that lacks psychotropic actions and is inactive at cannabinoid (CB) receptors, does not affect respiration or blood pressure when injected (1-2000 microg; 3.2-6360 nmol i.a.). Cannabidiol in doses up to 2 mg (6360 nmol) i.a. or i.v. did not affect the fall in mean blood pressure or the increase in ventilation (respiratory minute volume) caused by capsaicin and high doses of anandamide, responses that are mediated by activation of vanilloid VR1 (TRPV1) receptors in this species. Similar results were obtained with (-) cannabidiol (30-100 microg i.a.; 95-318 nmol). It has previously been shown using human embryonic kidney (HEK) cells over-expressing vanilloid human VR1 (hVR1) receptors that cannabidiol is a full agonist at vanilloid VR1 receptors in vitro. However, in the intact rat cannabidiol lacked vanilloid VR1 receptor agonist effects. We conclude that there are substantial functional differences between human and rat vanilloid VR1 receptors with respect to the actions of cannabidiol as an agonist at vanilloid VR1 receptors. Studies in vivo show that cannabidiol lacks any significant effect on mean blood pressure or respiratory minute volume when injected i.a. or i.v., and that this cannabinoid does not modulate the vanilloid VR1 receptor-mediated cardiovascular and ventilatory changes reflexly evoked by capsaicin or anandamide in rats anaesthetised with pentobarbital.

A novel synthetic, nonpsychoactive cannabinoid acid (HU-320) with antiinflammatory properties in murine collagen-induced arthritis

OBJECTIVE

To explore the antiarthritic potential of a novel synthetic cannabinoid acid, Hebrew University-320 (HU-320), in the DBA/1 mouse model of arthritis, and to investigate in vitro antiinflammatory and immunosuppressive effects of HU-320 on macrophages and lymphocytes.

METHODS

DBA/1 mice were immunized with bovine type II collagen (CII) to induce arthritis and then injected intraperitoneally daily with HU-320. The effects of treatment on arthritic changes in hind feet were assessed clinically and histologically, and draining lymph node responses to CII were assayed. Murine splenic and human blood lymphocytes were cultured to study the effect of HU-320 on polyclonal mitogenic stimulation. Macrophage cultures were set up to evaluate in vitro effects of HU-320 on production of tumor necrosis factor alpha (TNF alpha) and reactive oxygen intermediates (ROIs). The effect of HU-320 administration on lipopolysaccharide-induced serum TNF levels was assayed using C57BL/6 mice. Bioactive TNF production was measured using BALB/c clone 7 target cells. Evaluation of HU-320 psychoactivity was performed using established laboratory tests on Sabra mice.

RESULTS

Systemic daily administration of 1 and 2 mg/kg HU-320 ameliorated established CII-induced arthritis. Hind foot joints of treated mice were protected from pathologic damage. CII-specific and polyclonal responses of murine and human lymphocytes were down-modulated. HU-320 inhibited production of TNF from mouse macrophages and of ROIs from RAW 264.7 cells and suppressed the rise in serum TNF level following endotoxin challenge. HU-320 administration yielded no adverse psychotropic effects in mice.

CONCLUSION

Our studies show that the novel synthetic cannabinoid acid HU-320 has strong antiinflammatory and immunosuppressive properties while demonstrating no psychoactive effects. The profound suppressive effects on cellular immune responses and on the production of proinflammatory mediators all indicate its usefulness as a novel nonpsychoactive, synthetic antiinflammatory product.

Neuroprotective effect of cannabidiol, a non-psychoactive component from Cannabis sativa, on beta-amyloid-induced toxicity in PC12 cells

Abstract Alzheimer's disease is widely held to be associated with oxidative stress due, in part, to the membrane action of beta-amyloid peptide aggregates. Here, we studied the effect of cannabidiol, a major non-psychoactive component of the marijuana plant (Cannabis sativa) on beta-amyloid peptide-induced toxicity in cultured rat pheocromocytoma PC12 cells. Following exposure of cells to beta-amyloid peptide (1 micro g/mL), a marked reduction in cell survival was observed. This effect was associated with increased reactive oxygen species (ROS) production and lipid peroxidation, as well as caspase 3 (a key enzyme in the apoptosis cell-signalling cascade) appearance, DNA fragmentation and increased intracellular calcium. Treatment of the cells with cannabidiol (10(-7)-10(-4)m) prior to beta-amyloid peptide exposure significantly elevated cell survival while it decreased ROS production, lipid peroxidation, caspase 3 levels, DNA fragmentation and intracellular calcium. Our results indicate that cannabidiol exerts a combination of neuroprotective, anti-oxidative and anti-apoptotic effects against beta-amyloid peptide toxicity, and that inhibition of caspase 3 appearance from its inactive precursor, pro-caspase 3, by cannabidiol is involved in the signalling pathway for this neuroprotection.

Medicinal cannabis: is delta9-tetrahydrocannabinol necessary for all its effects?

Cannabis is under clinical investigation to assess its potential for medicinal use, but the question arises as to whether there is any advantage in using cannabis extracts compared with isolated Delta9-trans-tetrahydrocannabinol (Delta9THC), the major psychoactive component. We have compared the effect of a standardized cannabis extract (SCE) with pure Delta9THC, at matched concentrations of Delta9THC, and also with a Delta9THC-free extract (Delta9THC-free SCE), using two cannabinoid-sensitive models, a mouse model of multiple sclerosis (MS), and an in-vitro rat brain slice model of epilepsy. Whilst SCE inhibited spasticity in the mouse model of MS to a comparable level, it caused a more rapid onset of muscle relaxation, and a reduction in the time to maximum effect compared with Delta9THC alone. The Delta9THC-free extract or cannabidiol (CBD) caused no inhibition of spasticity. However, in the in-vitro epilepsy model, in which sustained epileptiform seizures were induced by the muscarinic receptor agonist oxotremorine-M in immature rat piriform cortical brain slices, SCE was a more potent and again more rapidly-acting anticonvulsant than isolated Delta9THC, but in this model, the Delta9THC-free extract also exhibited anticonvulsant activity. Cannabidiol did not inhibit seizures, nor did it modulate the activity of Delta9THC in this model. Therefore, as far as some actions of cannabis were concerned (e.g. antispasticity), Delta9THC was the active constituent, which might be modified by the presence of other components. However, for other effects (e.g. anticonvulsant properties) Delta9THC, although active, might not be necessary for the observed effect. Above all, these results demonstrated that not all of the therapeutic actions of cannabis herb might be due to the Delta9THC content.

Effects of cannabidiol (CBD) on regional cerebral blood flow

Animal and human studies have suggested that cannabidiol (CBD) may possess anxiolytic properties, but how these effects are mediated centrally is unknown. The aim of the present study was to investigate this using functional neuroimaging. Regional cerebral blood flow (rCBF) was measured at rest using (99m)Tc-ECD SPECT in 10 healthy male volunteers, randomly divided into two groups of five subjects. Each subject was studied on two occasions, 1 week apart. In the first session, subjects were given an oral dose of CBD (400 mg) or placebo, in a double-blind procedure. SPECT images were acquired 90 min after drug ingestion. The Visual Analogue Mood Scale was applied to assess subjective states. In the second session, the same procedure was performed using the drug that had not been administered in the previous session. Within-subject between-condition rCBF comparisons were performed using statistical parametric mapping (SPM). CBD significantly decreased subjective anxiety and increased mental sedation, while placebo did not induce significant changes. Assessment of brain regions where anxiolytic effects of CBD were predicted a priori revealed two voxel clusters of significantly decreased ECD uptake in the CBD relative to the placebo condition (p<0.001, uncorrected for multiple comparisons). These included a medial temporal cluster encompassing the left amygdala-hippocampal complex, extending into the hypothalamus, and a second cluster in the left posterior cingulate gyrus. There was also a cluster of greater activity with CBD than placebo in the left parahippocampal gyrus (p<0.001). These results suggest that CBD has anxiolytic properties, and that these effects are mediated by an action on limbic and paralimbic brain areas.

Effects of coadministration of cannabinoids and morphine on nociceptive behaviour, brain monoamines and HPA axis activity in a rat model of persistent pain

The antinociceptive effects of Delta9-tetrahydrocannabinol (Delta9-THC) have been widely described; however, its therapeutic potential may be limited by secondary effects. We investigated whether coadministration of low doses of cannabinoids or cannabinoids and morphine produced antinociception in the absence of side-effects. Effects of preadministration (i.p.) of Delta9-THC (1 or 2.5 mg/kg), cannabidiol (5 mg/kg), morphine (2 mg/kg), Delta9-THC + morphine, Delta9-THC + cannabidiol or vehicle on formalin-evoked nociceptive behaviour were studied over 60 min. Trunk blood and brains were collected 60 min after formalin injection and assayed for corticosterone and tissue levels of monoamines and metabolites, respectively. Drug effects on locomotor activity, core body temperature and grooming were assessed. Delta9-THC reduced both phases of formalin-evoked nociceptive behaviour, enhanced the formalin-evoked corticosterone response and increased the 4-hydroxy-3-methoxyphenylglycol : noradrenaline ratio in the hypothalamus. Cannabidiol alone had no effect on these indices and did not modulate the effects of Delta9-THC. Morphine reduced both phases of formalin-evoked nociceptive behaviour. Coadministration of Delta9-THC and morphine reduced the second phase of formalin-evoked nociceptive behaviour to a greater extent than either drug alone, and increased levels of thalamic 5-hydroxytryptamine. While the antinociceptive effects of Delta9-THC and morphine alone occurred at doses devoid of effects on locomotor activity, coadministration of Delta9-THC and morphine inhibited locomotor activity. In conclusion, coadministration of a low dose of morphine, but not cannabidiol, with Delta9-THC, increased antinociception and 5-hydroxytryptamine levels in the thalamus in a model of persistent nociception. Nevertheless, these enhanced antinociceptive effects were associated with increased secondary effects on locomotor activity.

Mustard oils and cannabinoids excite sensory nerve fibres through the TRP channel ANKTM1

Wasabi, horseradish and mustard owe their pungency to isothiocyanate compounds. Topical application of mustard oil (allyl isothiocyanate) to the skin activates underlying sensory nerve endings, thereby producing pain, inflammation and robust hypersensitivity to thermal and mechanical stimuli. Despite their widespread use in both the kitchen and the laboratory, the molecular mechanism through which isothiocyanates mediate their effects remains unknown. Here we show that mustard oil depolarizes a subpopulation of primary sensory neurons that are also activated by capsaicin, the pungent ingredient in chilli peppers, and by Delta(9)-tetrahydrocannabinol (THC), the psychoactive component of marijuana. Both allyl isothiocyanate and THC mediate their excitatory effects by activating ANKTM1, a member of the TRP ion channel family recently implicated in the detection of noxious cold. These findings identify a cellular and molecular target for the pungent action of mustard oils and support an emerging role for TRP channels as ionotropic cannabinoid receptors.

Effect of cannabinoids on lithium-induced vomiting in the Suncus murinus (house musk shrew)

RATIONALE

Marijuana has been reported to interfere with nausea and vomiting in chemotherapy patients. The principal cannabinoids found in marijuana include the psychoactive compound Delta-9-tetrahydrocannabinol (THC) and the non-psychoactive compound cannabidiol (CBD). The experiments reported here evaluated the potential of THC and CBD to interfere with vomiting in the Suncus murinus (house musk shrew) produced by lithium chloride (LiCl), which is the most commonly employed unconditioned stimulus for taste avoidance.

OBJECTIVES

To evaluate the potential of the principal components of marijuana, THC and CBD, to suppress Li-induced vomiting in the house musk shrew.

METHODS

Shrews were injected with vehicle or one of two cannabinoids [Delta-9-THC (1-20 mg/kg), or CBD (2.5-40 mg/kg)] 10 min prior to an injection of LiCl (390 mg/kg of 0.15 M) and were then observed for 45 min. The frequency of vomiting episodes and the latency to the first episode were measured. The role of the CB1 receptor in these effects was also evaluated by pretreatment with SR-141716.

RESULTS

Delta-9-THC produced a dose-dependent suppression of Li-induced vomiting, with higher doses producing greater suppression than lower doses. CBD produced a biphasic effect with lower doses producing suppression and higher doses producing enhancement of Li-induced vomiting. The suppression of Li-induced vomiting by THC, but not by CBD, was reversed by SR-141716.

CONCLUSIONS

These results indicate that two major cannabinoid compounds found in marijuana, THC and CBD, are effective treatments for Li-induced vomiting; however, only THC acts by the CB1 receptor. The effects of THC and CBD on vomiting were dose dependent; with THC the effect was linear, but with CBD the effect was biphasic.

Neuroprotective effect of (-)Delta9-tetrahydrocannabinol and cannabidiol in N-methyl-D-aspartate-induced retinal neurotoxicity: involvement of peroxynitrite

In glaucoma, the increased release of glutamate is the major cause of retinal ganglion cell death. Cannabinoids have been demonstrated to protect neuron cultures from glutamate-induced death. In this study, we test the hypothesis that glutamate causes apoptosis of retinal neurons via the excessive formation of peroxynitrite, and that the neuroprotective effect of the psychotropic Delta9-tetrahydroxycannabinol (THC) or nonpsychotropic cannabidiol (CBD) is via the attenuation of this formation. Excitotoxicity of the retina was induced by intravitreal injection of N-methyl-D-aspartate (NMDA) in rats, which also received 4-hydroxy-2,2,6,6-tetramethylpiperidine-n-oxyl (TEMPOL,a superoxide dismutase-mimetic), N-omega-nitro-L-arginine methyl ester (L-NAME, a nitric oxide synthase inhibitor), THC, or CBD. Retinal neuron loss was determined by TDT-mediated dUTP nick-end labeling assay, inner retinal thickness, and quantification of the mRNAs of ganglion cell markers. NMDA induced a dose- and time-dependent accumulation of nitrite/nitrate, lipid peroxidation, and nitrotyrosine (foot print of peroxynitrite), and a dose-dependent apoptosis and loss of inner retinal neurons. Treatment with L-NAME or TEMPOL protected retinal neurons and confirmed the involvement of peroxynitrite in retinal neurotoxicity. The neuroprotection by THC and CBD was because of attenuation of peroxynitrite. The effect of THC was in part mediated by the cannabinoid receptor CB1. These results suggest the potential use of CBD as a novel topical therapy for the treatment of glaucoma.

Antitumor Effects of Cannabidiol, a Nonpsychoactive Cannabinoid, on Human Glioma Cell Lines

Recently, cannabinoids (CBs) have been shown to possess antitumor properties. Because the psychoactivity of cannabinoid compounds limits their medicinal usage, we undertook the present study to evaluate the in vitro antiproliferative ability of cannabidiol (CBD), a nonpsychoactive cannabinoid compound, on U87 and U373 human glioma cell lines. The addition of CBD to the culture medium led to a dramatic drop of mitochondrial oxidative metabolism [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide test] and viability in glioma cells, in a concentration-dependent manner that was already evident 24 h after CBD exposure, with an apparent IC(50) of 25 microM. The antiproliferative effect of CBD was partially prevented by the CB2 receptor antagonist N-[(1S)-endo-1,3,3-trimethylbicyclo[2,2,1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528; SR2) and alpha-tocopherol. By contrast, the CB1 cannabinoid receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboximide hydrochloride (SR141716; SR1), capsazepine (vanilloid receptor antagonist), the inhibitors of ceramide generation, or pertussis toxin did not counteract CBD effects. We also show, for the first time, that the antiproliferative effect of CBD was correlated to induction of apoptosis, as determined by cytofluorimetric analysis and single-strand DNA staining, which was not reverted by cannabinoid antagonists. Finally, CBD, administered s.c. to nude mice at the dose of 0.5 mg/mouse, significantly inhibited the growth of subcutaneously implanted U87 human glioma cells. In conclusion, the nonpsychoactive CBD was able to produce a significant antitumor activity both in vitro and in vivo, thus suggesting a possible application of CBD as an antineoplastic agent.

Inhibitory effects of cannabinoid CB1 receptor stimulation on tumor growth and metastatic spreading: actions on signals involved in angiogenesis and metastasis

Stimulation of cannabinoid CB1 receptors by 2-methyl-arachidonyl-2'-fluoro-ethylamide (Met-F-AEA) inhibits the growth of a rat thyroid cancer cell-derived tumor in athymic mice by inhibiting the activity of the oncogene product p21ras. Here we report that Met-F-AEA also blocks the growth of tumors previously induced in nude mice by the s.c. injection of the same rat thyroid carcinoma cells. Met-F-AEA significantly inhibited, in tumors as well as transformed cells, the expression of the vascular endothelial growth factor, an angiogenetic factor known to be up-regulated by p21ras, as well as of one of its receptors, flt-1/VEGFR-1. The levels of the cyclin-dependent kinase inhibitor p27(kip1), which is down-regulated by p21ras, were instead increased by Met-F-AEA. All these effects were antagonized by the selective CB1 receptor antagonist SR141716A. Met-F-AEA inhibited in vitro the growth of a metastasis-derived thyroid cancer cell line more potently than a primary cancer cell line. Therefore, the hypothesis that CB1 receptor stimulation interferes not only with angiogenesis but also with metastatic processes was tested in a widely used model of metastatic infiltration in vivo, the Lewis lung carcinoma (3LL) in C57Bl/6 mice. Three weeks from the paw injection of 3LL cells, Met-F-AEA reduced significantly the number of metastatic nodes, in a way antagonized by SR141716A. Our findings indicate that CB1 receptor agonists might be used therapeutically to retard tumor growth in vivo by inhibiting at once tumor growth, angiogenesis, and metastasis.

Post-ischemic treatment with cannabidiol prevents electroencephalographic flattening, hyperlocomotion and neuronal injury in gerbils

The potential activity of cannabidiol, a non-psychoactive constituent of marijuana, in preventing damage caused by cerebral ischemia was studied. Cannabidiol (1.25-20 mg/kg) was given 5 min after 10 min bilateral carotid occlusion in freely-moving awake gerbils. Seven days after ischemia, it antagonized the electroencephalographic flattening of total spectral power, with a dose-dependent bell-shaped curve; the neuroprotective effect was greatest with 5 mg/kg. One day after ischemia cannabidiol completely antagonized ischemia-induced hyperlocomotion, at all doses. Rectal temperature did not change during the first hour after occlusion. Histological examination showed complete survival of CA1 neurons in cannabidiol-treated gerbils. These findings suggest a potential therapeutic role of cannabidiol in cerebral ischemia, though the clear mechanism of action remains to be elucidated.

Pharmacokinetics and pharmacodynamics of cannabinoids

Delta(9)-Tetrahydrocannabinol (THC) is the main source of the pharmacological effects caused by the consumption of cannabis, both the marijuana-like action and the medicinal benefits of the plant. However, its acid metabolite THC-COOH, the non-psychotropic cannabidiol (CBD), several cannabinoid analogues and newly discovered modulators of the endogenous cannabinoid system are also promising candidates for clinical research and therapeutic uses. Cannabinoids exert many effects through activation of G-protein-coupled cannabinoid receptors in the brain and peripheral tissues. Additionally, there is evidence for non-receptor-dependent mechanisms. Natural cannabis products and single cannabinoids are usually inhaled or taken orally; the rectal route, sublingual administration, transdermal delivery, eye drops and aerosols have only been used in a few studies and are of little relevance in practice today. The pharmacokinetics of THC vary as a function of its route of administration. Pulmonary assimilation of inhaled THC causes a maximum plasma concentration within minutes, psychotropic effects start within seconds to a few minutes, reach a maximum after 15-30 minutes, and taper off within 2-3 hours. Following oral ingestion, psychotropic effects set in with a delay of 30-90 minutes, reach their maximum after 2-3 hours and last for about 4-12 hours, depending on dose and specific effect. At doses exceeding the psychotropic threshold, ingestion of cannabis usually causes enhanced well-being and relaxation with an intensification of ordinary sensory experiences. The most important acute adverse effects caused by overdosing are anxiety and panic attacks, and with regard to somatic effects increased heart rate and changes in blood pressure. Regular use of cannabis may lead to dependency and to a mild withdrawal syndrome. The existence and the intensity of possible long-term adverse effects on psyche and cognition, immune system, fertility and pregnancy remain controversial. They are reported to be low in humans and do not preclude legitimate therapeutic use of cannabis-based drugs. Properties of cannabis that might be of therapeutic use include analgesia, muscle relaxation, immunosuppression, sedation, improvement of mood, stimulation of appetite, antiemesis, lowering of intraocular pressure, bronchodilation, neuroprotection and induction of apoptosis in cancer cells.

Taste avoidance and taste aversion: evidence for two different processes

The terms conditioned taste avoidance and conditioned taste aversion are often used interchangeably in the literature; however, considerable evidence indicates that they may represent different processes. Conditioned taste avoidance is measured by the amount that a rat consumes in a consumption test that includes both appetitive phases and consummatory phases of responding. However, conditioned taste aversion is more directly assessed with the taste reactivity test, which includes only the consummatory phase of responding. Rats display a conditioned taste aversion as conditioned rejection reactions (gapes, chin rubs, and paw treads) during an intraoral infusion of a nausea-paired flavored solution. Treatments that produce nausea are not necessary for the establishment of taste avoidance, but they are necessary for the establishment of taste aversion. Furthermore, treatments that alleviate nausea modulate neither the establishment nor the expression of taste avoidance, but they interfere with both the establishment and the expression of taste aversion. Considerable evidence exists indicating that these two measures are independent of one another. Taste avoidance may be motivated by conditioned fear rather than conditioned nausea, but taste aversion (as reflected by rejection reactions) may be motivated by conditioned nausea.

Design, synthesis, and biological evaluation of new inhibitors of the endocannabinoid uptake: comparison with effects on fatty acid amidohydrolase

A new series of arachidonic acid derivatives were synthesized and evaluated as inhibitors of the endocannabinoid uptake. Most of them are able to inhibit anandamide uptake with IC(50) values in the low micromolar range (IC(50) = 0.8-24 microM). In general, the compounds had only weak effects upon CB(1), CB(2), and VR(1) receptors (K(i) > 1000-10000 nM). In addition, there was no obvious relationship between the abilities of the compounds to affect anandamide uptake and to inhibit anandamide metabolism by fatty acid amidohydrolase (FAAH; IC(50) = 30-113 microM). This indicates that the compounds do not exert their effects secondarily to FAAH inhibition. It is hoped that these compounds, particularly the most potent in this series (compound 5, UCM707, with IC(50) values for anandamide uptake and FAAH of 0.8 and 30 microM, respectively), will provide useful tools for the elucidation of the role of the anandamide transporter system in vivo.

Vasodilator actions of abnormal-cannabidiol in rat isolated small mesenteric artery

1. The nonpsychoactive cannabinoid abnormal-cannabidiol (trans-4-[3-methyl-6-(1-methylethenyl)-2-cyclohexen-1-yl]-5-pentyl-1,3-benzenediol) (abn-cbd) produced concentration-dependent relaxation of methoxamine-precontracted rat small mesenteric artery. Endothelial removal reduced abn-cbd potency six-fold without affecting the maximum relaxation. 2. In endothelium-intact vessels, abn-cbd was less potent under 60 mM KCl-induced tone and inhibited by combination of L-N(G)-nitroarginine methyl ester (L-NAME) (nitric oxide synthase inhibitor; 300 micro M), apamin (small conductance Ca(2+)-activated K(+) channels inhibitor; 50 nM) and charybdotoxin (inhibitor of intermediate conductance Ca(2+)-activated K(+) channels and large conductance Ca(2+)-activated K(+) channels BK(Ca); 50 nM). L-NAME alone or in combination with either toxin alone had little effect. 3. In intact vessels, relaxations to abn-cbd were inhibited by SR 141716A (cannabinoid receptor antagonist; 1 or 3 micro M). Concomitant addition of L-NAME, apamin and charybdotoxin had no further effect. Other cannabinoid receptor antagonists either had little (SR 144528; 1 micro M and AM 251; 1 micro M) or no effect (AM 630; 10 micro M and AM 281; 1 micro M). Inhibition of gap junctions, G(i/o) protein coupling and protein kinase A also had no effect. 4. Endothelium-independent relaxation to abn-cbd was unaffected by L-NAME, apamin plus charybdotoxin or capsaicin (10 micro M). Abn-cbd inhibited CaCl(2)-induced contractions in vessels with depleted intracellular Ca(2+) stores and stimulated with methoxamine or KCl. This was insensitive to SR 141716A (3 micro M) but greatly reduced in vessels stimulated with ionomycin (Ca(2+) ionophore; 1 micro M). 5. We conclude that abn-cbd relaxes the rat small mesenteric artery by endothelium-dependent activation of K(+) channels via SR 141716A-sensitive pathways, which do not involve CB(1) and CB(2) receptors. It also causes endothelium-independent, SR 141716A-insensitive, relaxation by inhibiting Ca(2+) entry through voltage-gated Ca(2+) channels.

Plant-derived, synthetic and endogenous cannabinoids as neuroprotective agents. Non-psychoactive cannabinoids, 'entourage' compounds and inhibitors of N-acyl ethanolamine breakdown as therapeutic strategies to avoid pyschotropic effects

There is good evidence that plant-derived and synthetic cannabinoids possess neuroprotective properties. These compounds, as a result of effects upon CB(1) cannabinoid receptors, reduce the release of glutamate, and in addition reduce the influx of calcium following NMDA receptor activation. The major obstacle to the therapeutic utilization of such compounds are their psychotropic effects, which are also brought about by actions on CB(1) receptors. However, synthesis of the endogenous cannabinoids anandamide and 2-arachidonoylglycerol, which also have neuroprotective properties, are increased under conditions of severe inflammation and ischemia, raising the possibility that compounds that prevent their metabolism may be of therapeutic utility without having the drawback of producing psychotropic effects. In this review, the evidence indicating neuroprotective actions of plant-derived, synthetic and endogenous cannabinoids is presented. In addition, the pharmacological properties of endogenous anandamide-related compounds that are not active upon cannabinoid receptors, but which are also produced during conditions of severe inflammation and ischemia and may contribute to a neuroprotective action are reviewed.

The quest for a vascular endothelial cannabinoid receptor

This review examines pharmacological and biochemical evidence that suggests the existence of an as yet undefined endothelial receptor that mediates endocannabinoid-induced vasodilation. The signaling mechanisms triggered through this receptor and its potential physiological role are also discussed. Since vasodilation is often associated with hypotension, mechanisms involved in the hypotensive actions of cannabinoids, including the endocannabinoids anandamide and 2-arachidonoylglycerol, are also briefly reviewed.

(-)-Cannabidiol antagonizes cannabinoid receptor agonists and noradrenaline in the mouse vas deferens

The nonpsychoactive plant cannabinoid, (-)-cannabidiol, modulates in vivo responses to Delta(9)-tetrahydrocannabinol. We have found that cannabidiol can also interact with cannabinoid CB(1) receptor agonists in the mouse vas deferens, a tissue in which prejunctional cannabinoid CB(1) receptors mediate inhibition of electrically evoked contractions by suppressing noradrenaline and/or ATP release. Cannabidiol (0.316-10 microM) attenuated the ability of (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (R-(+)-WIN55212) to inhibit contractions in a concentration-related, surmountable manner with a K(B) value (120.3 nM) well below its reported cannabinoid receptor CB(1)/CB(2) K(i) values. Cannabidiol (10 microM) also antagonized (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol (CP55940; K(B)=34 nM) and [D-Ala(2), NMePhe(4), Gly-ol]enkephalin (DAMGO; K(B)=5.6 microM) and attenuated contractile responses to noradrenaline, phenylephrine and methoxamine but not to beta, gamma-methyleneadenosine 5'-triphosphate. At 3.16-10 microM, it increased the amplitude of evoked contractions, probably by enhancing contractile neurotransmitter release. We conclude that cannabidiol antagonizes R-(+)-WIN55212 and CP55940 by acting at prejunctional sites that are unlikely to be cannabinoid CB(1) or CB(2) receptors.

Cannabidiol: an overview of some pharmacological aspects

Over the past few years, considerable attention has focused on cannabidiol (CBD), a major nonpsychotropic constituent of cannabis. The authors present a review on the chemistry of CBD and discuss the anticonvulsive, antianxiety, antipsychotic, antinausea, and antirheumatoid arthritic properties of CBD. CBD does not bind to the known cannabinoid receptors, and its mechanism of action is yet unknown. It is possible that, in part at least, its effects are due to its recently discovered inhibition of anandamide uptake and hydrolysis and to its antioxidative effect.

Cannabinoid modulation of sensory neurotransmission via cannabinoid and vanilloid receptors: roles in regulation of cardiovascular function

Capsaicin-sensitive sensory nerves are widely distributed in the cardiovascular system. They are activated by a variety of physical and chemical stimuli, characteristically by capsaicin acting via the vanilloid receptor VR1, and have a role in the regulation of peripheral vascular resistance and maintenance of homeostasis via their afferent and efferent functions. Cannabinoids, a recently discovered family of extracellular signalling molecules, can act at cannabinoid (CB) receptors expressed on sensory nerves, to cause inhibition of sensory neurotransmitter release. There is recent evidence, however, that anandamide, an endogenous cannabinoid, can activate VR1, coexpressed with CB receptors on the same sensory nerve terminals, causing a release of sensory neurotransmitter, vasorelaxation and hypotension. Hence, anandamide can elicit opposite actions, inhibition via CB receptors and excitation via VR1, on sensory neurotransmission. The possible biological significance of this is discussed.

Delta 9-tetrahydrocannabinol and cannabinol activate capsaicin-sensitive sensory nerves via a CB1 and CB2 cannabinoid receptor-independent mechanism

Although Delta(9)-tetrahydrocannabinol (THC) produces analgesia, its effects on nociceptive primary afferents are unknown. These neurons participate not only in pain signaling but also in the local response to tissue injury. Here, we show that THC and cannabinol induce a CB(1)/CB(2) cannabinoid receptor-independent release of calcitonin gene-related peptide from capsaicin-sensitive perivascular sensory nerves. Other psychotropic cannabinoids cannot mimic this action. The vanilloid receptor antagonist ruthenium red abolishes the responses to THC and cannabinol. However, the effect of THC on sensory nerves is intact in vanilloid receptor subtype 1 gene knock-out mice. The THC response depends on extracellular calcium but does not involve known voltage-operated calcium channels, glutamate receptors, or protein kinases A and C. These results may indicate the presence of a novel cannabinoid receptor/ion channel in the pain pathway.